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Partager le résultat de cette recherche Interroger des sources externesEtude paramétrique des échanges convectifs turbulents dans les configurations d’intérêt pratique / Ridha Mebrouk
Titre : Etude paramétrique des échanges convectifs turbulents dans les configurations d’intérêt pratique Type de document : texte imprimé Auteurs : Ridha Mebrouk, Auteur ; Abderrahim Boudenne, Directeur de thèse ; Yassine Kabar, Directeur de thèse Editeur : جامعة الإخوة منتوري قسنطينة Année de publication : 2017 Importance : 139 f. Format : 30 cm. Note générale : 2 copies imprimées disponibles
Langues : Français (fre) Catégories : Français - Anglais
Génie MécaniqueTags : Convection turbulente Simulation numérique Nanofluide Enceinte chauffée par le bas,
Convection forcée Echanges turbulents Echangeur de chaleur Transfert thermique conjugué Turbulent convection Numerical simulation Nanofluid Enclosure heated from below Forced
convection Turbulent exchanges Heat exchanger Conjugate heat transfer الحمل المضطرب؛ المحاكاة العددیة؛ نانومائع؛ تجویفات مسخنة من الأسفل؛ الحمل القسري؛ التبادل المضطرب، المبادلات
الحراریة؛نقل الحرارة المترافقةIndex. décimale : 620 Génie Mécanique Résumé : This thesis presents the results of two studies: the first concerns natural turbulent convection in a
rectangular cavity heated from the bottom wall and filled with a nanofluid and the second relates to the
investigation of conjugate heat transfer in a fin-and-tube heat exchanger.
The cavity of the first study is tall and has a heat source embedded on its bottom wall, while its left, right
and top walls are maintained at a relatively low temperature. The working fluid is a water based nanofluid
having three nanoparticle types: alumina, copper and copper oxide. The influence of pertinent parameters
such as the Rayleigh number, the type of nanofluid and solid volume fraction of nanoparticles on the cooling
performance is studied. Steady forms of two dimensional Reynolds-Averaged-Navier-Stokes equations and
conservation equations of mass and energy, coupled with the Boussinesq approximation, are solved by the
control volume based discretisation method employing the SIMPLE algorithm for pressure-velocity
coupling. Turbulence is modeled using the standard k-ε model. The Rayleigh number, Ra, is varied from
2.49x1009 to 2.49x1011. The volume fractions of nanoparticles were varied in the interval 0≤φ≤ 6% . Stream
lines, isotherms, velocity profiles and Temperature profiles are presented for various combinations of Ra,
the type of nanofluid and solid volume fraction of nanoparticles. The results are reported in the form of
average Nusselt number on the heated wall. It is shown that for all values of Ra, the average heat transfer
rate from the heat source increases almost linearly and monotonically as the solid volume fraction increases.
Finally the average heat transfer rate takes on values that decrease according to the ordering Cu, CuO and
Al2O3.
In the second study we determined the heat transfer and friction characteristics of a realistic fin-andtube heat exchanger . The computations assume steady-state heat transfer and fluid flow. Nusselt number
and friction factor characteristics of the heat exchanger are presented for various values of Reynolds
numbers. The energy conservation and the heat conduction equations in 3 dimensions have been solved
in the fluid and the solid respectivelyalong with the mass and momentum conservation equations in order
to determine these characteristics. Both laminar and turbulent flow regimes are considered. The effect of
turbulence modeling was investigated using three different models (the one equation Spalart-Allmaras
turbulence model, the standard k-ε model and the RSM model). The computations allowed the
determination of the dynamic and thermal fields. Model validation was carried out by comparing the
calculated friction factor f and Colburn j-factor to experimental results found in the literature. The
plotted results showed a qualitatively good agreement between numerical results and experimental data. The
results obtained also showed that the simplest of the three turbulence models tested(i.e. SpalartAllmaras) gives the closest values to the experimental data
Diplôme : Doctorat en sciences En ligne : ../theses/gmecanique/MEB7154.pdf Format de la ressource électronique : Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=10428 Etude paramétrique des échanges convectifs turbulents dans les configurations d’intérêt pratique [texte imprimé] / Ridha Mebrouk, Auteur ; Abderrahim Boudenne, Directeur de thèse ; Yassine Kabar, Directeur de thèse . - جامعة الإخوة منتوري قسنطينة, 2017 . - 139 f. ; 30 cm.
2 copies imprimées disponibles
Langues : Français (fre)
Catégories : Français - Anglais
Génie MécaniqueTags : Convection turbulente Simulation numérique Nanofluide Enceinte chauffée par le bas,
Convection forcée Echanges turbulents Echangeur de chaleur Transfert thermique conjugué Turbulent convection Numerical simulation Nanofluid Enclosure heated from below Forced
convection Turbulent exchanges Heat exchanger Conjugate heat transfer الحمل المضطرب؛ المحاكاة العددیة؛ نانومائع؛ تجویفات مسخنة من الأسفل؛ الحمل القسري؛ التبادل المضطرب، المبادلات
الحراریة؛نقل الحرارة المترافقةIndex. décimale : 620 Génie Mécanique Résumé : This thesis presents the results of two studies: the first concerns natural turbulent convection in a
rectangular cavity heated from the bottom wall and filled with a nanofluid and the second relates to the
investigation of conjugate heat transfer in a fin-and-tube heat exchanger.
The cavity of the first study is tall and has a heat source embedded on its bottom wall, while its left, right
and top walls are maintained at a relatively low temperature. The working fluid is a water based nanofluid
having three nanoparticle types: alumina, copper and copper oxide. The influence of pertinent parameters
such as the Rayleigh number, the type of nanofluid and solid volume fraction of nanoparticles on the cooling
performance is studied. Steady forms of two dimensional Reynolds-Averaged-Navier-Stokes equations and
conservation equations of mass and energy, coupled with the Boussinesq approximation, are solved by the
control volume based discretisation method employing the SIMPLE algorithm for pressure-velocity
coupling. Turbulence is modeled using the standard k-ε model. The Rayleigh number, Ra, is varied from
2.49x1009 to 2.49x1011. The volume fractions of nanoparticles were varied in the interval 0≤φ≤ 6% . Stream
lines, isotherms, velocity profiles and Temperature profiles are presented for various combinations of Ra,
the type of nanofluid and solid volume fraction of nanoparticles. The results are reported in the form of
average Nusselt number on the heated wall. It is shown that for all values of Ra, the average heat transfer
rate from the heat source increases almost linearly and monotonically as the solid volume fraction increases.
Finally the average heat transfer rate takes on values that decrease according to the ordering Cu, CuO and
Al2O3.
In the second study we determined the heat transfer and friction characteristics of a realistic fin-andtube heat exchanger . The computations assume steady-state heat transfer and fluid flow. Nusselt number
and friction factor characteristics of the heat exchanger are presented for various values of Reynolds
numbers. The energy conservation and the heat conduction equations in 3 dimensions have been solved
in the fluid and the solid respectivelyalong with the mass and momentum conservation equations in order
to determine these characteristics. Both laminar and turbulent flow regimes are considered. The effect of
turbulence modeling was investigated using three different models (the one equation Spalart-Allmaras
turbulence model, the standard k-ε model and the RSM model). The computations allowed the
determination of the dynamic and thermal fields. Model validation was carried out by comparing the
calculated friction factor f and Colburn j-factor to experimental results found in the literature. The
plotted results showed a qualitatively good agreement between numerical results and experimental data. The
results obtained also showed that the simplest of the three turbulence models tested(i.e. SpalartAllmaras) gives the closest values to the experimental data
Diplôme : Doctorat en sciences En ligne : ../theses/gmecanique/MEB7154.pdf Format de la ressource électronique : Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=10428 Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité MEB/7154 MEB/7154 Thèse Bibliothèque principale Thèses Disponible
Titre : Investigation des échanges convectifs dans diverses configurations Type de document : texte imprimé Auteurs : Issam Rezaiguia, Auteur ; Mahfoud Kadja, Directeur de thèse Editeur : constantine [Algérie] : Université Constantine 1 Année de publication : 2014 Importance : 142 f. Format : 30 cm. Note générale : 2 copies imprimées disponibles
Langues : Français (fre) Catégories : Français - Anglais
Génie MécaniqueTags : convection naturelle nanofluides cavité triangulaire angle d'inclinaison simulation numérique microcanaux chute de pression transfert thermique conjugué fraction solide comportement non-Newtonien natural convection nanofluids triangular cavity inclination angle numerical simulation microchannels pressure drop conjugate heat transfer solid fraction non-Newtonian behavior الحمل الحراري الطبيعي مائع نانوي تجويف ثلاثي الشكل زاوية الميل محاكاة العددية قنوات ميكروية هبوط الضغط نقل الحرارة نسب الحيود للذرات الصلبة سلوك غير نيوتوني Index. décimale : 620 Génie Mécanique Résumé : This thesis reports the results of two studies: the first one concerns natural convection in isosceles triangular cavities with a partially active base while the second one concerns heat transfer in microchannels.
The first study considers natural convection cooling of a heat source located on the bottom wall of an inclined isosceles triangular enclosure filled with a Cu water-nanofluid. The right and left walls of the enclosure are both maintained cold at constant equal temperatures, while the remaining parts of the bottom wall are insulated. The study has been carried out for a Rayleigh number in the range 104 ≤ Ra ≤ 106, for a heat source length in the range 0.2 ≤ ε ≤ 0.8, for a solid volume fraction in the range 0.0 ≤ � ≤ 06 and for an inclination angle in the range 00 ≤ δ ≤ 450. Results are presented in the form of streamline contours, isotherms, maximum temperature at the heat source surface and average Nusselt number. It is noticed that the addition of Cu nanoparticles enhances the heat transfer rate and therefore cooling effectiveness for all values of Rayleigh number, especially at low values of Ra. The effect of the inclination angle becomes more noticeable as one increases the value of Ra. For high Rayleigh numbers, a critical value for the inclination angle of δ = 150 is found for which the heat source maximum temperature is highest.
The second study investigates heat transfer in microchannels machined in heat dissipating sinks. The fluid used is a nanofluid whose properties are temperature dependent. The energy dissipation is evaluated for various solid fraction contents along with the cooling effectiveness of this modern type of heat exchangers. The shape of the channels is also investigated. The evaluation parameter used for thermal energy dissipation is the Nusselt number while that used for cooling effectiveness is the static pressure drop between the inlet and the outlet of the microchannel. Conjugate convection-conduction energy conservation equations have been solved along with mass and momentum conservation equations in order to determine these parameters.
The results obtained showed important heat transfer augmentation with solid fraction at the expense of an increased pressure drop, i.e high pumping cost (therefore low cooling effectiveness). The microchannel inlet section geometry was also found to contribute to the values of the Nusselt number and pressure drop. Among the tested geometries (elliptical, rectangular, trapezoidal) the rectangular section provided the best compromise between heat transfer augmentation and pumping cost. At the end of the study, a comparison was made between the results obtained by assuming Newtonian rheology and those obtained with non-Newtonian rheological behavior of the same nanofluid sample. It was found that the assumption of non-Newtonian rheological behavior of nanofluids gives higher Nusselt number values and much lower pressure drops.
Diplôme : Doctorat en sciences En ligne : ../theses/gmecanique/REZ6773.pdf Format de la ressource électronique : Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=9837 Investigation des échanges convectifs dans diverses configurations [texte imprimé] / Issam Rezaiguia, Auteur ; Mahfoud Kadja, Directeur de thèse . - constantine [Algérie] : Université Constantine 1, 2014 . - 142 f. ; 30 cm.
2 copies imprimées disponibles
Langues : Français (fre)
Catégories : Français - Anglais
Génie MécaniqueTags : convection naturelle nanofluides cavité triangulaire angle d'inclinaison simulation numérique microcanaux chute de pression transfert thermique conjugué fraction solide comportement non-Newtonien natural convection nanofluids triangular cavity inclination angle numerical simulation microchannels pressure drop conjugate heat transfer solid fraction non-Newtonian behavior الحمل الحراري الطبيعي مائع نانوي تجويف ثلاثي الشكل زاوية الميل محاكاة العددية قنوات ميكروية هبوط الضغط نقل الحرارة نسب الحيود للذرات الصلبة سلوك غير نيوتوني Index. décimale : 620 Génie Mécanique Résumé : This thesis reports the results of two studies: the first one concerns natural convection in isosceles triangular cavities with a partially active base while the second one concerns heat transfer in microchannels.
The first study considers natural convection cooling of a heat source located on the bottom wall of an inclined isosceles triangular enclosure filled with a Cu water-nanofluid. The right and left walls of the enclosure are both maintained cold at constant equal temperatures, while the remaining parts of the bottom wall are insulated. The study has been carried out for a Rayleigh number in the range 104 ≤ Ra ≤ 106, for a heat source length in the range 0.2 ≤ ε ≤ 0.8, for a solid volume fraction in the range 0.0 ≤ � ≤ 06 and for an inclination angle in the range 00 ≤ δ ≤ 450. Results are presented in the form of streamline contours, isotherms, maximum temperature at the heat source surface and average Nusselt number. It is noticed that the addition of Cu nanoparticles enhances the heat transfer rate and therefore cooling effectiveness for all values of Rayleigh number, especially at low values of Ra. The effect of the inclination angle becomes more noticeable as one increases the value of Ra. For high Rayleigh numbers, a critical value for the inclination angle of δ = 150 is found for which the heat source maximum temperature is highest.
The second study investigates heat transfer in microchannels machined in heat dissipating sinks. The fluid used is a nanofluid whose properties are temperature dependent. The energy dissipation is evaluated for various solid fraction contents along with the cooling effectiveness of this modern type of heat exchangers. The shape of the channels is also investigated. The evaluation parameter used for thermal energy dissipation is the Nusselt number while that used for cooling effectiveness is the static pressure drop between the inlet and the outlet of the microchannel. Conjugate convection-conduction energy conservation equations have been solved along with mass and momentum conservation equations in order to determine these parameters.
The results obtained showed important heat transfer augmentation with solid fraction at the expense of an increased pressure drop, i.e high pumping cost (therefore low cooling effectiveness). The microchannel inlet section geometry was also found to contribute to the values of the Nusselt number and pressure drop. Among the tested geometries (elliptical, rectangular, trapezoidal) the rectangular section provided the best compromise between heat transfer augmentation and pumping cost. At the end of the study, a comparison was made between the results obtained by assuming Newtonian rheology and those obtained with non-Newtonian rheological behavior of the same nanofluid sample. It was found that the assumption of non-Newtonian rheological behavior of nanofluids gives higher Nusselt number values and much lower pressure drops.
Diplôme : Doctorat en sciences En ligne : ../theses/gmecanique/REZ6773.pdf Format de la ressource électronique : Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=9837 Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité REZ/6773 REZ/6773 Thèse Bibliothèque principale Thèses Disponible
Titre : Comparaison des schémas numériques de discrétisation des premier et second ordre : application à la convection dans un conduit cylindrique Type de document : texte imprimé Auteurs : Fatima Zohra Ferahta, Auteur ; M. Afrid, Directeur de thèse Editeur : Constantine : Université Mentouri Constantine Année de publication : 2008 Importance : 97 f. Note générale : 01 Disponible à la salle de recherche 02 Disponibles au magazin de la B.U.C. 01 CD Langues : Français (fre) Catégories : Français - Anglais
PhysiqueTags : Photovolaique Ecoulement laminaire Simulation numérique Transfert thermique Convectuion mixte Conduit cylindrique Conjugué Volume fini mixed convection cylinder duct laminar flow conjugate heat transfer numerical simulation finite volume المترافق الحراري التحويلالرقائقي الجريان اسطواني أنبوب المختلط الحمل المنتهية الحجوم العددية المحاكات Index. décimale : 530 Physique Résumé : This study concerns the flow of a Newtonian and incompressible fluid in a horizontal cylindrical duct uniformly heated at the wall. The associated heat transfer modes are mixed convection in the fluid and conduction in the wall. Thermophysical fluid properties are thermo-dependant. A three dimensional numerical simulation is conducted, The finite volumes method with a second order scheme in time and space is adopted to resolve this problem, Two different heating conditions are considered: strenght of electrical current of 45 an 65 Amperes which correspond to two various Graschof numbers: Gr=244492 and 510000. The other control parameters such Reynolds and Prandtl numbers are fixed constant: Re=606 and Pr=8. The transversal secondary flow in a cross section is induced by a bouyancy effect along the duct. In a cross straight section, two contra-rotative cells are observed. These rolls are separated by the median vertical plane. The center of these rolls moves downward when the axial coordinate increases. The major points of this work consist first at a qualitative and a quantitative comparison between the results obtained by the first and the second order schemes, then a comparison with experimental results is achieved. It is to be noted that, qualitatively the first and the second order schemes give similar results but quantitatively the results obtained by the first order scheme are closer to the experimental results. These differences induce more important discrepancies of the axial Nusselt number. This is due to the fact that the second order scheme needs a more refined mesh than the first order on one hand and on other hand in the experimental results the uncertainties and the heat losses are not known. Taking into account these comments could reduce the difference between the obtained results. Diplôme : Magistère En ligne : ../theses/physique/FER5221.pdf Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=3462 Comparaison des schémas numériques de discrétisation des premier et second ordre : application à la convection dans un conduit cylindrique [texte imprimé] / Fatima Zohra Ferahta, Auteur ; M. Afrid, Directeur de thèse . - Constantine : Université Mentouri Constantine, 2008 . - 97 f.
01 Disponible à la salle de recherche 02 Disponibles au magazin de la B.U.C. 01 CD
Langues : Français (fre)
Catégories : Français - Anglais
PhysiqueTags : Photovolaique Ecoulement laminaire Simulation numérique Transfert thermique Convectuion mixte Conduit cylindrique Conjugué Volume fini mixed convection cylinder duct laminar flow conjugate heat transfer numerical simulation finite volume المترافق الحراري التحويلالرقائقي الجريان اسطواني أنبوب المختلط الحمل المنتهية الحجوم العددية المحاكات Index. décimale : 530 Physique Résumé : This study concerns the flow of a Newtonian and incompressible fluid in a horizontal cylindrical duct uniformly heated at the wall. The associated heat transfer modes are mixed convection in the fluid and conduction in the wall. Thermophysical fluid properties are thermo-dependant. A three dimensional numerical simulation is conducted, The finite volumes method with a second order scheme in time and space is adopted to resolve this problem, Two different heating conditions are considered: strenght of electrical current of 45 an 65 Amperes which correspond to two various Graschof numbers: Gr=244492 and 510000. The other control parameters such Reynolds and Prandtl numbers are fixed constant: Re=606 and Pr=8. The transversal secondary flow in a cross section is induced by a bouyancy effect along the duct. In a cross straight section, two contra-rotative cells are observed. These rolls are separated by the median vertical plane. The center of these rolls moves downward when the axial coordinate increases. The major points of this work consist first at a qualitative and a quantitative comparison between the results obtained by the first and the second order schemes, then a comparison with experimental results is achieved. It is to be noted that, qualitatively the first and the second order schemes give similar results but quantitatively the results obtained by the first order scheme are closer to the experimental results. These differences induce more important discrepancies of the axial Nusselt number. This is due to the fact that the second order scheme needs a more refined mesh than the first order on one hand and on other hand in the experimental results the uncertainties and the heat losses are not known. Taking into account these comments could reduce the difference between the obtained results. Diplôme : Magistère En ligne : ../theses/physique/FER5221.pdf Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=3462 Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité FER/5221 FER/5221 Thèse Bibliothèque principale Thèses Disponible
Titre : Etude des améliorations des nombres de nusselt par l’utilisation de nanofluides ou changement de la géométrie Type de document : texte imprimé Auteurs : Rabah Nebbati, Auteur ; Mahfoud Kadja, Directeur de thèse Editeur : جامعة الإخوة منتوري قسنطينة Année de publication : 2017 Importance : 144 f. Format : 30 cm. Note générale : 2 copies imprimées disponibles
Langues : Français (fre) Catégories : Français - Anglais
PhysiqueTags : Nanofluid Micro-channel Heat Sink Conjugate Heat Transfer Forced
Convection Heat Transfer Enhancement النانومائع مبدد الحرارة – میكروقناة الإنتقال الحراري المتزاوج الحمل القسري تعزیز الحمل الحراريIndex. décimale : 530 Physique Résumé : This Ph. D. thesis work reports the results of the study of the laminar forced
convective heat transfer flow in two different geometries: A geometry made with two coaxial
discs and a micro-channels heat sink. This study is numerical and is based on a finite volume
single-phase approach and was achieved using the mixture (water- /γ-Al2O3 ) as nonofluid.
The flows are modeled using the Navier Stokes equations along with the energy conservation
equation in the fluid domain and the heat conduction equation in the solid domain. The
thermophysical properties used (thermal conductivity and dynamic viscosity) were assumed
constant or temperature dependent. The thermal and dynamic fields resulting from our
calculations show an increase in the local and average Nusselt number, in the average radial
heat transfer coefficient, in the relative radial heat transfer coefficient and in the average shear
stress at the contact interfaces with increasing Reynolds number. We also noted that the
increase in heat flux, the addition of nanoparticles in the base fluid, the assumption of
temperature dependent properties and the change in the entry cross section of the channels
significantly affect these fields. This improvement of heat transfer using nanofluids may
therefore give birth to a promising new technology which manufactures very compact heat
exchangers to be used particularly in the domain of power electronicsDiplôme : Doctorat en sciences En ligne : ../theses/physique/NEB7069.pdf Format de la ressource électronique : Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=10532 Etude des améliorations des nombres de nusselt par l’utilisation de nanofluides ou changement de la géométrie [texte imprimé] / Rabah Nebbati, Auteur ; Mahfoud Kadja, Directeur de thèse . - جامعة الإخوة منتوري قسنطينة, 2017 . - 144 f. ; 30 cm.
2 copies imprimées disponibles
Langues : Français (fre)
Catégories : Français - Anglais
PhysiqueTags : Nanofluid Micro-channel Heat Sink Conjugate Heat Transfer Forced
Convection Heat Transfer Enhancement النانومائع مبدد الحرارة – میكروقناة الإنتقال الحراري المتزاوج الحمل القسري تعزیز الحمل الحراريIndex. décimale : 530 Physique Résumé : This Ph. D. thesis work reports the results of the study of the laminar forced
convective heat transfer flow in two different geometries: A geometry made with two coaxial
discs and a micro-channels heat sink. This study is numerical and is based on a finite volume
single-phase approach and was achieved using the mixture (water- /γ-Al2O3 ) as nonofluid.
The flows are modeled using the Navier Stokes equations along with the energy conservation
equation in the fluid domain and the heat conduction equation in the solid domain. The
thermophysical properties used (thermal conductivity and dynamic viscosity) were assumed
constant or temperature dependent. The thermal and dynamic fields resulting from our
calculations show an increase in the local and average Nusselt number, in the average radial
heat transfer coefficient, in the relative radial heat transfer coefficient and in the average shear
stress at the contact interfaces with increasing Reynolds number. We also noted that the
increase in heat flux, the addition of nanoparticles in the base fluid, the assumption of
temperature dependent properties and the change in the entry cross section of the channels
significantly affect these fields. This improvement of heat transfer using nanofluids may
therefore give birth to a promising new technology which manufactures very compact heat
exchangers to be used particularly in the domain of power electronicsDiplôme : Doctorat en sciences En ligne : ../theses/physique/NEB7069.pdf Format de la ressource électronique : Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=10532 Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité NEB/7069 NEB/7069 Thèse Bibliothèque principale Thèses Disponible
